arXiv subjects

Haruhiko Terao

Publications and source records attributed to Haruhiko Terao.

At least 19 recordsLinked to original sources

arXiv2016

Nonperturbative evaluation of quantum particle production in parametric resonance enhanced by noise

Numerical studies are reported to support the idea to explain the particle production in late inflationary era based on the parametric resonance with a noise effect. Two nonperturbative renormalization group formulations are used to numerically calculate the time evolution of particle numbers. Firstly, the dynamical renormalization group (DRG) method is applied to sum up the secular contributions. Secondly, we derive an exact evolution equation of the particle number which turned out to be possible surprisingly owing to the presence of the noise effect. Our numerical results show a drastic enhancement of the particle production in agreement with earlier works qualitatively. A comparison is made of numerical results based on two methods. Our work provides nonperturbative and quantitative methods to evaluate the particle production for the inflationary cosmology.

hep-ph↗

arXiv2011

Fixed point merger in the SU(N) gauge beta functions

We discuss qualitative behavior of the SU(N) gauge beta functions in QCD with many massless flavors. Non-perturbative beta functions can be obtained by extracting the renormalized trajectories in the exact renormalization group framework. We examine the renormalization group equations for the general four-fermi couplings as well as the gauge coupling obtained in a simple approximation scheme. It is shown that the gauge beta function possesses not only an IR but also a UV fixed point in the conformal window. These fixed points merge with each other and disappear at the edge of the conformal window. The scaling dimensions of the quark mass operator at the fixed points are also shown.

hep-ph↗

arXiv2008

Duality cascade of softly broken supersymmetric theories

We study the duality cascade of softly broken supersymmetric theories. We investigate the renormalization group (RG) flow of SUSY breaking terms as well as supersymmetric couplings. It is found that the magnitudes of SUSY breaking terms are suppressed in most regimes of the RG flow through the duality cascade. At one stage of cascading, the gaugino mass of the strongly coupled sector and scalar masses converge to certain values, which are determined by the gauge coupling and the gaugino mass of the weakly coupled sector. At the next stage, the strongly and weakly coupled sectors are interchanged with each other. We also show the possibility that cascading would be terminated by the gauge symmetry breaking, which is induced by the so-called B-term.

hep-th↗

arXiv2007

Conformal dynamics in gauge theories via non-perturbative renormalization group

The dynamics at the IR fixed point realized in the $SU(N_c)$ gauge theories with massless Dirac fermions is studied by means of the non-perturbative renormalization group. The analysis includes the IR fixed points with non-trivial Yukawa couplings. The renormalization properties of the scalar field are also discussed and it is shown that hierarchical mass scale may be allowed without intense fine-tuning due to a large anomalous dimension.

hep-ph↗

arXiv2007

Higgs and Top quark coupled with a conformal gauge sector

We propose a dynamical scenario beyond the standard model, in which the radiative correction to the Higgs mass parameter is suppressed due to a large anomalous dimension induced through a conformal invariant coupling with an extra gauge sector. Then the anomalous dimension also suppresses the Yukawa couplings of the Higgs field. However, the large top Yukawa coupling can be generated effectively through mixing among top quarks and the fermions of the conformal gauge sector. This scenario is found to predict a fairly heavy Higgs mass of about 500 GeV. We present an explicit model and show consistency with the Electro-Weak precision measurements of the S and T parameters as well as the Z boson decay width.

hep-ph↗

arXiv2006

Fine-tuning in gauge mediated supersymmetry breaking models and induced top Yukawa coupling

It is shown that fine-tuning of the Higgs parameters stronger than a few % is required at the best in the models with gauge mediated supersymmetry breaking. With the aim of solving this problem, we consider a new type of models in which the top Yukawa coupling is induced at TeV scale through mass mixing with unknown matter fields. Then it is found that the fine-tuning problem can be eliminated essentially. We discuss some phenomenological features of this model and also consider the extension to the next-to-minimal models.

hep-ph↗

arXiv2006

Dynamical realization of democratic Yukawa matrices and alignment of A-terms

We study realization of the democratic form of Yukawa matrices by infrared fixed points. We investigate renormalization-group flows of Yukawa couplings in models with a single Yukawa matrix for three families, and up and down-sector Yukawa matrices. It is found that each model has its certain pattern of renormalization-group flows of Yukawa matrices. We apply them to the charged lepton sector and quark sector, and show that realistic results for the second and third families are obtained with natural initial conditions, e.g. $(V_{MNS})_{23} \sim 2/\sqrt{6}$, $m_s/m_b \sim V_{cb} \sim m_μ/m_τ$ and $m_c/m_t \sim (m_s/m_b)^{3/2}$. We also study corresponding A-terms. The A-terms approach toward the universal form with no physical CP-violating phase. Thus, constraints due to various neutral flavor changing processes except for $μ\to e γ$ are found to be satisfied by this dynamics. In order to suppress the electric dipole moments as well as $μ\to e γ$ sufficiently, more alignment of the A-terms with some reason is required.

hep-ph↗

arXiv2005

Induced top Yukawa coupling and suppressed Higgs mass parameters

In the scenarios with heavy top squarks, mass parameters of the Higgs field must be fine-tuned due to a large logarithmic correction to the soft scalar mass. We consider a new possibility that the top Yukawa coupling is small above TeV scale. The large top mass is induced from strong Yukawa interaction of the Higgs with another gauge sector, in which supersymmetry breaking parameters are given to be small. Then it is found that the logarithmic correction to the Higgs soft scalar mass is suppressed in spite of the strong coupling and the fine-tuning is ameliorated. We propose an explicit model coupled to a superconformal gauge theory which realizes the above situation.

hep-ph↗

arXiv2004

Democratic mass matrices induced by strong gauge dynamics and large mixing angles for leptons

We consider dynamical realization of the democratic type Yukawa coupling matrices as the Pendelton-Ross infrared fixed points.?Such fixed points of the Yukawa couplings become possible by introducing many Higgs fields, which are made superheavy but one massless mode. Explicitly, we consider a strongly coupled GUT based on $SU(5) \times SU(5)$, where rapid convergence to the infrared fixed point generates sufficiently large mass hierarchy for quarks and leptons. Especially, it is found that the remarkable difference between mixing angles in the quark and lepton sectors may be explained as a simple dynamical consequence. We also discuss a possible scenario leading to the realistic mass spectra and mixing angles for quarks and leptons. In this scheme, the Yukawa couplings not only for top but also for bottom appear close to their quasi-fixed points at low energy and, therefore, $\tan β$ should be large.

hep-ph↗

arXiv2004

Large Mass Scale by Strong Gauge Dynamics with Infrared Fixed Point

We consider a mechanism for realizing the desired decoupling of strongly-coupled sector which is supposed to generate hierarchical structure of the Yukawa couplings. In our mechanism, the same strongly-coupled sector is responsible for generating a sufficiently flat potential and a large vacuum expectation value (VEV) of a gauge-singlet scalar field by suppressing its soft scalar mass and self-coupling. Vacuum instability is caused by supersymmetry-breaking A-term of order 10 TeV. We explicitly demonstrate the infrared convergence of soft scalar masses due to strongly-coupled dynamics and show the soft mass of the singlet is at most comparable to soft masses of squarks and sleptons, which are much suppressed than the A-term. The physical mass scale of the decoupling is calculated in a self-consistent way. We also reinterpret the result in terms of a RG-improved effective potential.

hep-ph↗

arXiv2004

Suppressed supersymmetry breaking terms in the Higgs sector

We study the little hierarchy between mass parameters in the Higgs sector and other SUSY breaking masses. This type of spectrum can relieve the fine-tuning problem in the MSSM Higgs sector. Our scenario can be realized by superconformal dynamics. The spectrum in our scenario has significant implications in other phenomenological aspects like the relic abundance of the lightest neutralino and relaxation of the unbounded-from-below constraints.

hep-ph↗

arXiv2003

Softening the Supersymmetric Flavor Problem in Orbifold GUTs

The infra-red attractive force of the bulk gauge interactions is applied to soften the supersymmetric flavor problem in the orbifold SU(5) GUT of Kawamura. Then this force aligns in the infra-red regime the soft supersymmetry breaking terms out of their anarchical disorder at a fundamental scale, in such a way that flavor-changing neutral currents as well as dangerous CP-violating phases are suppressed at low energies. It is found that this dynamical alignment is sufficiently good compared with the current experimental bounds, as long as the diagonalization matrices of the Yukawa couplings are CKM-like.

hep-ph↗

arXiv2003

Exact $S_3$ symmetry solving the supersymmetric flavor problem

The exact discrete flavor symmetry, $S_3$ in the hadronic sector and $S_3 \times Z_2$ in the leptonic sector, which has been recently found, is introduced in a supersymmetric extension of the standard model. We investigate the supersymmetric flavor problem, and explicitly find that thanks to the flavor symmetry the dangerous FCNC processes and CP-violating phases are sufficiently suppressed.

hep-ph↗

arXiv2002

Flavor violation in supersymmetric theories with gauged flavor symmetries

In this paper we study flavor violation in supersymmetric models with gauged flavor symmetries. There are several sources of flavor violation in these theories. The dominant flavor violation is the tree-level $D$-term contribution to scalar masses generated by flavor symmetry breaking. We present a new approach for suppressing this phenomenologically dangerous effects by separating the flavor-breaking sector from supersymmetry-breaking one. The separation can be achieved in geometrical setups or in a dynamical way. We also point out that radiative corrections from the gauginos of gauged flavor symmetries give sizable generation-dependent masses of scalars. The gaugino mass effects are generic and not suppressed even if the dominant $D$-term contribution is suppressed. We also analyze the constraints on the flavor symmetry sector from these flavor-violating corrections.

hep-ph↗

arXiv2002

Suppressing FCNC and CP-Violating Phases with Extra Dimensions

The infrared attractiveness of soft-supersymmetry breaking (SSB) parameters is investigated in extra dimensions. The SSB parameters are assumed to run from the Planck scale M_{PL} down to the GUT scale M_{GUT}. We find that, even for M_{PL}/M_{GUT}=100, the SSB parameters in six dimensions can align out of their anarchical disorder at M_{PL} in such a way that flavor-changing neutral currents as well as dangerous CP-violating phases are sufficiently suppressed at M_{GUT}. A concrete, realistic example based on SU(5) in six dimensions is presented.

hep-ph↗

arXiv2002

Non-Perturbative Renormalization Group Analysis in Quantum Mechanics

We analyze quantum mechanical systems using the non-perturbative renormalization group (NPRG). The NPRG method enables us to calculate quantum corrections systematically and is very effective for studying non-perturbative dynamics. We start with anharmonic oscillators and proceed to asymmetric double well potentials, supersymmetric quantum mechanics and many particle systems.

quant-ph↗

arXiv2002

Suppressing FCNC and CP-Violating Phases by Extra Dimensions

In extra dimensions the infrared attractive force of gauge interactions is amplified. We find that this force can align in the infrared limit the soft-supersymmetry breaking terms out of their anarchical disorder at a fundamental scale, in such a way that flavor-changing neutral currents as well as dangerous CP-violating phases are sufficiently suppressed at the unification scale. The main assumption is that the matter and Higgs supermultiplets and the flavor-dependent interactions such as Yukawa interactions are stuck at the four-dimensional boundary. As a concrete example we consider the minimal model based on SU(5) in six dimensions.

hep-ph↗

arXiv2002

Yukawa Hierarchy Transfer Based on Superconformal Dynamics and Geometrical Realization in String Models

We propose a scenario that leads to hierarchical Yukawa couplings and degenerate sfermion masses at the same time, in the context of extra-dimensional models, which can be naturally embedded in a wide class of string models. The hierarchy of Yukawa couplings and degeneracy of sfermion masses can be realized thanks to superconformal gauge dynamics. The sfermion mass degeneracy is guaranteed by taking the superconformal fixed point to be family independent. In our scenario, the origin of Yukawa hierarchy is attributed to geometry of compactified dimensions and the consequent volume dependence of gauge couplings in the superconformal sectors. The difference in these gauge couplings is dynamically transferred to the hierarchy of the Yukawa couplings. Thus, our scenario combines a new dynamical approach and the conventional geometrical approach to the supersymmetric flavor problem.

hep-ph↗